Our objective is to understand the relationship between structure and function in the nervous system. We will study the functional significance of neurons in the cat's visual cortex which respond preferentially to stimuli of a particular orientation to determine: 1) the origin of the orientation-specific response of a particular neuron, 2) whether it can be modified by sensory stimulation, and 3) what its behavioral significance is. Development of orientation-sensitive responses will be studied by chronically recording from single cells in the visual cortex of young kittens. The animal's visual experience will be carefully controlled during development to evaluate whether sensory stimulation determines, modifies, or simply maintains the orientation-specific response of individual neurons. Secondly, we will examine the influence of visual experience on the distribution of different types of orientation-sensitive cells in the visual cortex. We will use acute recording techniques to study the columnar organization of the visual cortex in animals that have been exposed only to a restricted set of stimuli during their development. Thirdly, we will test whether the shape of cortical cell receptive fields is determined by the animal's visual experience. We will raise animals under conditions of restricted visual experience and compare the shape of their cortical receptive fields to the configuration of the stimuli to which they were exposed during their development. Finally, in a series of behavioral tests we will study the functional significance of orientation-sensitive cells in the intact animal. This involves simplifying cortical physiology by raising the cats in a restricted visual environment and testing whether this produces corresponding changes in the animal's visual capabilities.